22, 15 & 10mm Rad Pipes

[Amateur]

Hi all.

I just wanted to know what effect, if any, it will have on my combi heating system replacing some of the 10mm pipes to my rads with 15mm?

Its a bungalow and the boiler is piped up to span most of the loft in 22mm. This is then stepped to 15mm and then to 10mm for the drops down to the rads.

Previous owner buried the 10mm copper pipe in the plaster with no plastic protective wrap so I am keen to remove them asap as we are having most rooms replastered anyway.

There are two rads in the living room and one in the hall with buried 10mm plastic pipe which will not be replaced. Also there are three more in trunking mounted 10mm copper that will stay.

I want to replace some of the 10mm drops with 15mm chrome surface mounted as i have already done in the kitchen. All heating is working fine at the moment with the kitchen in 15mm but i wanted to double check if replacing more of the 10mm with 15mm wether or not it would effect the performance of the rest of the system that is still 10mm? I hope this makes sense.

Cheers

 

[Last Plumber]

Are you replacing all of the drops?

 

[Amateur]

Are you replacing all of the drops?

No, 6 rads will stay on the existing 10mm drops and 4 will be changed to 15mm if its ok?

 

[Amateur]

The loft space is pretty tight at 4ft max at the apex hence why 10mm has been used previously to make it easier to feed up/down deep in the eaves.

 

[Last Plumber]

You will reduce the frictional resistance in the sections of your heating system which will be fed by the new 15mm pipes.

You may find that these sections can rob the 10mm sections of water/flow rate, and reduce the performance of those 10mm sections.

You should be able to check down the lock shield side of the rads of the 15mm sections in order to re-balance the system.

However, it is not always that straight forward and I would advise you to get a Heating Engineer to look over it.

 

[Amateur]

I was wondering if i would need to get into balancing.

Thanks for the quick reply. Maybe a rethink then although i will still need to get out and replace the 10mm from the plaster before it pin holes and leaks.

 

[Best]

10mm pipe can only be run short distances to each radiator.
Drops can be just about okay as they are probably only about 6metres long (flow and return combined). But any greater length will make the rads slow at heating and perhaps not perform properly the colder the weather gets.
I prefer the 15mm pipes, but as Last Plumber warns, the easier flow on 15mm pipes will rob flow to the 10mm pipes unless the system is balanced.

 

[Amateur]

10mm pipe can only be run short distances to each radiator.
Drops can be just about okay as they are probably only about 6metres long (flow and return combined). But any greater length will make the rads slow at heating and perhaps not perform properly the colder the weather gets.
I prefer the 15mm pipes, but as Last Plumber warns, the easier flow on 15mm pipes will rob flow to the 10mm pipes unless the system is balanced.

Each 10mm leg in the converted garage is about 9m long, no wonder its always the slowest to heat up then.

 

[BG Tech]

i would change all the drops to 15mm then rebalance rads

 

[Kargo]

Leave the 10mm, they will be fine. Don't stress, balancing the system isn't too difficult. Just open all lock shields and TRVs and warm heating system from cold. Go around and feel which radiators get warm first. Turn the lock shield on the 'first warm' radiator all the way down and then back open 1/4 turn. Next warm rad lock shield all the way down and back open 1/2 turn. Next 3/4 turn and so on. Usually doing 3 or 4 rads is enough to get adequate balance. There is a more technical and precise way to balance heating systems but this is usually adequate.

 

[Best]

The 9m long 10mm legs are not going to work well.

 

[Amateur]

I have to replace pipework to a few rads as the 10mm is buried in the plaster which I dont want to have skimmed over and then wait for it to pin hole. Also they are fed up through the eaves too so i dont fancy waiting for them to freeze.

I wanted to replace the 10mm where i could in 15mm by repositioning rads and rerouting pipework to a more central position in the loft. Its a fairly shallow pitched roof so the easier it is to access the pipes the better.

Its just as long as the system can be balanced with 10mm & 15mm pipes really.